Is it possible to upload other types of files, such as figures, PDFs, MS Word documents, MS Excel spreadsheets, FlowJo workspaces, etc?

Yes, certainly. Any file that is not an FCS file is best included as an attachment. There is an attachments panel about half way down on your experiment overview page. You can use the 'Choose File' button to select a file on your computer, and then the 'Upload button' to upload it as an attachment to your experiment. You can have as many attachments as you need, and you can provide those with a human readable description.

Experiment attachments